This invention relates to a copper alloy material for lead frames for semiconductor devices, and more particularly to a copper alloy material which is excellent in strength and thermal-exfoliation resistance of a solder applied on the leads, as well as stamping-die wear resistance, i.e., property of reducing the wear of stamping dies used for stamping outlead frames from a strip of the copper alloy material.
Conventionally, Cu alloys having a typical composition consisting essentially by weight of 2% Sn, 0.2% Ni, and 0.05% P have been widely used as materials for lead frames (hereinafter called as "lead frame material(s)") for semiconductor devices such as IC's, LSI's, and VLSI's.
However, in recent years, it has been required for lead frame materials to possess further improved strength for use as lead frames, so as to cope with the demand for improved performance or efficiency and increased wiring densities of semiconductor devices. The above-mentioned conventional copper alloy lead frame materials are fairly excellent in repeated-bending strength, thermal conductivity and electrical conductivity, platability, and solderability (soldering adhesion), but do not possess sufficient strength and are therefore unable to fully exhibit these properties. Furthermore, they are not satisfactory in respect of thermal-exfoliation resistance of a solder applied on the leads and hence have low solderability of the semiconductor devices. Still further, from the viewpoint of economy a demand has arisen for improving the wear resistance of dies used for stamping copper alloy lead frames, to reduce the manufacturing cost.